| Managing excess soil water in agricultural fields in the Northern Great Plains through subsurface drainage increases the risk of sodification in high-risk soils. Leaching sodic soils with low electrical conductivity (EC) water, rainfall, may result in the swelling of soil, dispersion of clay particles and consequently the breakdown of soil structure leading to changes in physical and mechanical properties of soils (e.g., reduced infiltration, hard-setting and reduced trafficability). In this dissertation, the effectiveness of calcium amendments of gypsum and spent lime, a byproduct of the processing sugar beets, with water-management treatments of free drainage (FD) and no drainage (ND) on improving physical properties of the soil were examined.;The first objective was to evaluate the effects of drainage and surface treatments on the penetration resistance (PR). The second objective was to use infiltration tests with a mini-disk tension infiltrometer and a Cornell sprinkle infiltrometer to investigate changes in hydraulic properties. Lastly, a drawbar dynamometer was used to measure draft on a chisel plow as it was pulled across the plots by a tractor equipped with an auto-guidance system and instrumentation interfaced with the controller area network of the tractor.;The results show that the PR values of plots with gypsum application at high rate of 22.4 Mg ha-1 (GH) were significantly higher than other surface amendments. GH increased the hydraulic conductivity of the soil matrix compared to spent lime application at rate of 22.4 Mg ha-1 (SL); however, the overall flow of water through the soil profile, including the soil matrix and the macropores, was not affected. Both GH and gypsum application at high rate of 11.2 Mg ha-1 (GL) lowered the drawbar power requirements compared to spent lime application. For many farmers, drainage enables early planting and the adding of ameliorants will safeguard against further sodification of their fields. |
